Hardened cellular or fibrous friction elements and method of producing same



Patented June 24, 1930 UNITED STATES PATENT OFFICE IZADOB J'. NOVAK, OI BRIDGEP ORT, CONNECTICUT, ASSIGNOR, BY IEFNE ASSIGN- MENTSjTO BAYBESTOS-MANHATTAN, INC.', ,A. CORPORATION O1! NEW JERSEY HARDENED CELLULAR 01B, YFIIBBOUS FRICTION ELEMENTS AN D METHOD OF PRODUCING- 1 SAME Io Drawing.

This invention relates. to improvements in hardened cellular or fibrous friction elements and methods of producing same, and more especially friction elements with a base of woven or unwoven stock, in which the .bindin substance comprises an infusible phenollc condensation product and a medlfying substance.

I am aware that it has previously been proposed to utilize phenolic condensation products in friction elements, see Frood British Patent No. 121,301, which employs an infusible phenol resin as the sole binder, and Fisher, U. S. Patent No. 1,436,158, who utilizes a mixture of phenol resin and sufficient rosin to augment the frictional properties of the phenol resin. These. are essentially the only two types of binder intended for, friction elements comprising phenol go resin which have come to my notice, but both have serious drawbacks for this use.

The hardening phenol resins used by both Frood and Fisher and defined by the condensing agents .used, have been found to display marked tendencies to form a hard permanent glaze under frictional abuse, the frictional coeflicient frequently falling to as low as .09 for an asbestos body containing only an infusible type phenol resin as binder. Friction elements with such a minimum coefficient would not be satisfactory in. the present desi n of clutches and brakes whibh are intende to operate efliciently at a frictional 'coeflicient between .2 and .35. Fisher .-seeks to'improve upon'the Frood binder by addinga frictionvaugmenting substance and "as'a' practical method of carrying out his f'process describes a combination of phenol.

yresin 'androsin. I-Ief thereby obtains an inm-crea'se' in the frictional properties of the binder, but in so doing and in proportion Y to the amount ofrosin';"lad ded (up to of the mixture; as determined by the applicant-for optimumfr'ictional qualities) he 5 transformsi'hiscombination into a fusible soluble resin which hasno ;longerthe strong, hard,- hea' t resisting properties-of an'i'nfusi- 4 ble phenolic resin. "Berend U. S. Patent No.

1,191,390 describes this combinatipn of gumso and phenolic; resin in a method of produc- Application filed June 9, 1926f. Serial No. 114,849.

ing fusible soluble resins. In short, Frood has a strong, hard infusible resin which shows low frictional qualities, while Fisher obtains ood frictional qualities at the expense of the strength and heat resisting properties of his resin mixture.

In carrying out my invention, I utilize as a binder a homogeneous stable solution of a phenolic resin in a suitable modifying carrier hereinafter described. The binder may 0 be imprefgnated into a suitable asbestos base either 0 the woven or unwoven type, or mixed with the fibrous materials comprising the base previously to forming. The saturated formed element may be then subj ected to heat and oxidation, or to heat without oxidation until the desired hardness and toughness has been attained through setting of the phenolic resin to a substantially infusible state with or without hardening of the modifying substance.

The treatment used may be varied so as to bring out the desirable qualities conferred by the particular modifier being used: for instance, china wood oil may be heat-treated so as to oxidize or polymerize it, the two processes conferring different qualities on the resultant product; or a non-dryin oil maybe destructively distilled, oxidize or allowed to remain 1n its original form to so utilize its softening properties on the resultant substantially infusible phenolic resin.- The use of the combination of phenolic resin and modifier treated according to the present invention permits of the production 35 of modified resin binders having a large range of frictional and strength characteristics from which suitable products may be chosen to suit the needs of the friction element industry. 0' The following illustration of one methodfor making unwoven clutch facings, may be given: Annular ring blanks of the approximate desired dimensions may be die-cut from asbestos'millboard and may be allowed to saturate;- preferably 'under pressure) 7 to an increase in weight of 50% 1n a saturantj and china wood oil.

com posecl of.{equal parts of a smooth solu- I tion of cresylic acid formaldehyde resin",

After" saturation, the- I fic purpose of increasing the frictional qualiharden the surfaces so that they will not' adhere in the subsequent operation. The rings may be then stacked face to face and held together in a pack by suitable means,

for instance, a set of steel plates and a bolt running therethrough, and subjected to a temperature of say 350 F. more or less, for say 6 hours more or less, followed by say 400 F. more or less for say 4 hours more or less.

During this period the phenolic resinchina wood oil binder has hardened due to the setting of the resin and the polymerization of the china wood oil, and the rings when removed from the pack are hard and strong. The rings may be then sanded to remove the surfaces, which always contain an excess of saturant and may be then returned to the ovens for a further cure of say 4 hours more or less, at say 350 F. more or less. This last cure serves the specities o the resultant clutch facings. The rings removed from the pack may show a low minimum friction after sanding, whereas after the final cure the minimum friction is much augmented.

By another variation of the above described method, I may proceed as follows: The saturated blanks (linseed oil may replace china wood oil here) may be hung in an oven on racks and heated at say 250 F. more or less, for say 4 hours more or less, and at say 350 F. more or less for say 10 hours more. or less, durin which time the hardening of the binder ue to the setting of the resin and the oxidation of the oil takes place progressively without any distortion or bhstering of ring surfaces, which might be expected considerin that we are subjecting a phenolic resin 0 the infusible type to hlgh temperature without any application of pressure to confine the evolved gases. After the rings are sufficiently hard, the may be removed from the ovens, cooled un er pressure to maintain flatness, and

sanded to size. No friction augmenting cure is necessary in this case. The hardness is of the same order as that of the rings cured in a pack.

For woven clutch facings, I preferably vary the saturant so as to decrease the concentration of the binder, since this type of facing is usually desired flexible and resilicut. The following may be an example of ai suitable saturant:

. I y Parts Boiled linseed oil 80 Phenolic resin r 20 Benz'olln 200 The woven asbestos. covered wire tape is be then subjected to a temperature of say' 300 F. more or less, for say 5 hours more.

or less, the spiral removed from the mandrel and cured further for say 1 hour more or less, at say 300 F.- more or less. The

rin s may be then cut from the spiral, laced an pressed. The surfaces may be ground if such a finish is desired.

Clutch facings made by the first two methods above are eminently suited for the cfitting of gear teeth in their outer or inner circumferences where it is desired that the very marked in these products due to the excellent cohesion and uniform toughness of material made in the manner described. Also, I find it perfectly practical to cure thiclmesses of as great as one inch thoroughly and uniformly, without the case hardened effect noticeable in treatments previously used for friction elements, where the hardening depends on oxidation or destructive distillation from the surface inwards.

Another feature of thisinvention resides in the high durability combined with frictional eflicienc of the resultant elements as compared wit previous "commercial products. Where I may 'utilize a combination of drying oil and phenolic resin for these processes, I obtain the toughening effect of the drying oil modified by the strength and cohesiveness so characteristic of the infusible type of phenolic resins, these properties combining to develop marked resistance to destructlve abrasion even under temperatures as high as say, 700 F. more or less, which cause the breakdown of almost all other friction materials known to the art. At lower temperatures, the durability is increased, and for normal automotive use in a properly designed clutch, these facings will outlast the car.

Again, these treatments may be utilized for the manufacture of brake linings where it is desired to produce a friction material of high durability, low com ressibility, and freedom from grabbing ten encies, either of the ri 'd or flexible type. Materials of these speci cations. are now-considered essential meepsa width may be saturated to say 50% increase Frictional'quality refers to a group of in weight in a saturant of the following desirable characteristics in friction material illustrative composition:

- Parts Phenolic resin 60 China wood oil 40 They may be allowed to surface dry in an .next cured in an oven at say 350 F. for

six hours and at 400 F. more or less for say 4hours. The straps may be then removed and while the segments still adhere to the drums'a further cure of say 2 hours at 350 F. more or less is administered to develop the frictional qualities ofthe open surface. After completion of the cure the formed strips are removed from the drums (the adhesion is very slight), and the edges are machined to remove roughness. They -are now ready for use.

Woven brake lining may be treated in a similar manner starting with woven asbestos metallic tape to produce a rigid product, or the saturant may be thinnedwith a suitable solvent to produce semi-rigid or flexible ings. For certain uses it is'desirable to decrease the synthetic resin hardener and vary the oil by the use of various gums, waxes, asphalts or tars. For instance, a satisfactory treatment for a flexible woven brake lining may consist of 20 parts resin and'80 parts 'of water gas tar, the whole cured at 400 F. more or less, in festoons until sufliciently hard.

Another type of satisfactory treatment may consist in Parts Oil soluble phenolic resin 20 Gilsonite 80' Benzol 150 With this treatment, the treated is merely dried at a low temperature 200 F. more or less, to remove the solvent, and .the hardening of the phenolic resin is allowed to take place gradually under heatdeveloped in service. This treatment obviates the necessity of subjecting the brake lining to high temperatures of cure with their attendant inconveniences.

infusible type in combination with an oil,

asphalt, gum, tar, or any substance which tional quality; for instance, the most satisfactory frictional material now in use on than was previously considered necessary. Frictional uality therefore depends entirely upon the a ility of the frictlonal material to maintain throughout its life a substantially constant co-efficient of friction under the various mechanical conditions of use and abuse.

I claim as my invention:

1. A method of producing elements adapted for frictional purposes,,.comprising modern internal brakes has a lower friction lmpregnating an incombustible fibrous base with a saturant comprising phenolic resin capable of transformation by heat to an infusible binder and a modifier capable per se of also becoming a binder under the conditions of cure, and thereafter heat treating the saturated incombustible fibrous base to render, the saturantinfusible and produce an element havin satisfactory frictional quality, said modi er being of such a character that the'resultant binder is infusible.

2. A- method of producing elements adapted for frictional purposes, comprising impregnating an incombustible fibrous base with a saturant comprising'phenolic resin capable of transformation] by heat to an infustible binder, and a modifier capable per se of also becoming -a binder under the conditions of cure, and thereafter heat treating the saturated incombustible fibrous base to render the saturant infusible and produce an element having satisfactory frictional quality, said modifier comprising china wood oil of such character that the resultant binder is infusible.

3. A new article of manufacture adapted for frictional purposes comprising an incombustible fibrous base impregnated with an infusible phenolic resin binder containing a modifying material which per se is also a binder, the latter being of such a type that the resultant binder is infusible and the product has satisfactory frictional quantity,

said product being substantially uniform in hardness throughout its thickness.

4. A new article of manufacture adapted for frictional purposes comprising an incomdoes not prevent the synthetic resin from F bustible fibrous base impregnated with an becoming infusible, and the products resulting from this composite saturant when combined' with and hardened in an incombustible fibrous or cellular base, whether woven oiunwoven.

- infusible phenolic resin modified by hardened china wood oil, said roduct possessing satisfactory frictional qua ity and being substantially uniform in hardness throughout its thickness.

5. As a new article of manufacture .a uniformly hardened structure havin frictional quality, comprising an incombustlble fibrous base impregnated with a. binder comprising infusible phenolic resin and a, polymerizd china wood oil.

IZADOR J. NOVAK. 

